that rescue effort is changing quickly now, more than 70 people stranded as we've been reporting here. Everything they've tried so far hasn't worth. Now they plan to chopper in to get them out. Abc's lidsy davis with the hour by hour. Reporter: Tonight a window of opportunity to rescue the 74 people stranded on this ship in the antarctic. The maritime safety authority says weather conditions have improved making it possible to air lift passengers in groups of 12 by helicopter. This, just the latest in a number of rescue attempts since the first distress message went out one week ago. Earlier in the week three ice breaking ships tried to tear through the miles of thick ice unsuccessfully with just ten miles to go, punishing weather forced the rescuers to turn back. It's raining, heavy winds, very poor visibility. Reporter: The current plan is to fly all 52 passengers to the chinese ice breaker and from there transported by barge to the australian ice breaker waiting just a few miles away, but the operation is complex, involving a number of steps. The biggest factor of all, weather. Those rescue operations will require seven flights in all. Based on the current weather forecast, they have a little less than 36 hours to complete this portion of the operation which is expected to take at least five hours, but again, all of this, david, extremely deponent on the weather. Seven flights, thank you.

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